Kawasaki Syndrome (KS) is an acute febrile vasculitis of infancy and early childhood that can result in permanent coronary artery damage (aneurysms, stenosis, and ectasia) in 20% of patients. The etiology of this disease is currently unknown although there is general agreement that an infectious agent is responsible. Attention has recently been given to the T and B cell abnormalities characteristic of KS patients during the acute phase of their illness. By analogy to known viral diseases (EBV, HTLV I and HTLV III), it has been postulated that infection with a lymphotropic virus with affinity for endothelial and lymphoid cells might explain the vasculitis and immunologic abnormalities associated with KS. It is the purpose of this research proposal to examine the possibility that a lymphotropic virus may be present in the peripheral blood lymphocytes (PBL) of patients with KS. Culture supernatants of PBL will be screened for reverse transcriptase and DNA polymerase activity by standard techniques. The polymerase activity will be characterized with respect to divalent cation, template, and primer specificity. Co-cultivation with different continuous T cell lines will be attempted. Immunofluorescence, electron microscopy, and DNA cloning and hybridization techniques will also be applied to this project.